Evidence for the existence of a proteasome in Toxoplasma gondii: intracellular localization and specific peptidase activities.

The proteasome is a large intracellular protein complex whose main function is proteolytic removal of damaged proteins. It has recently been shown that the proteasome has a crucial role in the pathogenesis of protozoan parasites. We attempted to characterize the proteasome of T. gondii (RH strain). In immunoblot experiments, we showed that MCP231 monoclonal antibody, directed against the human 20S proteasome, labelled homologous proteins in T. gondii with a pattern similar to that observed in mammalian cells. The study of in vitro proteolytic activities showed that chymotrypsin-like activity (the only activity obtained with archaebacteria) was present in Toxoplasma, with Km and specific activity values close to those observed with eukaryotic cells. Immunofluorescence studies showed that the Toxoplasma proteasome predominated in the cytosol.     

Spatial structure of litter-dwelling ant distribution in a subtropical dry forest

Understanding the spatial patterns of species distribution is essential to characterize the structure of communities, to optimize species inventories and to evaluate the impact of biotic and abiotic variables. Here we describe the spatial structure of the distribution of leaf litter ant species, and of biotic factors that could explain it, in a subtropical semi-deciduous forest of the Argentinian Chaco, characterized by a dense understorey of shrubs and terrestrial bromeliads. Environmental variables (leaf litter quantity and ground bromeliad density) were measured and ants were collected in 1 m² quadrats distributed along two 200 m transects at intervals of 1.25 m. Overall 87 species were collected. Sixteen positive associations and a single negative association were observed between the 11 most frequent species taken pair-wise. Our results suggest that the spatial distribution of leaf litter ants was determined at two different scales. At a small scale (period below 10 m) a periodic spatial structure, likely due to intraspecific competition, produced a succession of peaks of abundance separated by gaps. At a larger scale (period around 50 m), periodically distributed environmental factors induced aggregates of colonies of species responding positively to these factors. A high quantity of leaf litter and, to a lesser extent, a high density of ground bromeliads promoted a high density and a high species richness of ants. Numerically dominant ants being generally positively associated, interspecific competition was apparently weak. All ant species whose abundance was correlated with an environmental factor were not completely spatially structured by it. This suggests that some other factors, such as intraspecific competition, may have counter-effects. Received 14 March 2005; revised 26 April 2005; accepted 10 May 2005.     

The potential mechanisms involved in the anti-carcinogenic action of probiotics

Probiotic bacteria are live microbial food ingredients that provide a health benefit to the consumer. In the past it was suggested that they served to benefit the host primarily through the prevention of intestinal infections. More recent studies have implicated probiotic bacteria in a number of other beneficial effects within the host including: *The suppression of allergies. *Control of blood cholesterol levels. *Modulation of immune function. *And the prevention of cancers of the colon. The reputed anti-carcinogenic effect of probiotics arises from in vivo studies in both animals and to a limited extent in man; this evidence is supported by in vitro studies with carcinoma cell lines and anti-mutagenicity assays. However, the mechanisms involved in any effect have thus far been difficult to elucidate; studies offer evidence for a variety of mechanisms; we have reviewed these and come to the opinion that, the anti-carcinogenic effect may not be attributable to a single mechanism but rather to a combination of events not yet fully elucidated or understood.     

Caste morphology and development in Termitogeton nr. planus (Insecta,Isoptera, Rhinotermitidae)

The termite family Rhinotermitidae displays a wide diversity in its patterns of social organization in castes. The genus Termitogeton probably branched off early in the evolution of this family. We studied the developmental pathways of a putative undescribed species from New Guinea, Termitogeton nr planus. The development begins with two white inactive instars (larvae), the second of which possesses small wing buds. These are followed by a relatively homogenous group of active immature stages (pseudergates) among which a biometric study revealed the presence of four instars. The first of these instars possesses wing buds that regress at subsequent molts. The external morphology of older instars resembles that of higher termite workers. Older pseudergates can differentiate into presoldiers and then into soldiers, but they are also able to molt into a unique stage with long wing pads (nymph), preceding the imago. Colony maturity can be reached with about 10(3) individuals. The sex ratio is near 1:1 in all castes except soldiers, among which females are more numerous than males. The caste pattern of T. nr. planus is reminiscent of those of the Kalotermitidae and Termopsidae, and of Prorhinotermes among the Rhinotermitidae. None of these taxa possess a true worker caste, permanently diverted from imaginal development: social tasks are done by unspecialized immatures that retain a full array of developmental options, including that of proceeding to the imago. The most remarkable trait of T. nr. planus is the presence in all second-instar individuals of wing buds that later regress to reappear in the single nymphal stage. We suggest that the traditional definitions of the terms larvae, nymphs, and pseudergates should be revised because they cannot be satisfactorily applied to the castes of Termitogeton.     

Inhibition of HIV-1 replication by cell-penetrating peptides binding Rev

New therapeutic agents able to block HIV-1 replication are eagerly sought after to increase the possibilities of treatment of resistant viral strains. In this report, we describe a rational strategy to identify small peptide sequences owning the dual property of penetrating within lymphocytes and of binding to a protein target. Such sequences were identified for two important HIV-1 regulatory proteins, Tat and Rev. Their association to a stabilizing domain consisting of human small ubiquitin-related modifier-1 (SUMO-1) allowed the generation of small proteins named SUMO-1 heptapeptide protein transduction domain for binding Tat (SHPT) and SUMO-1 heptapeptide protein transduction domain for binding Rev (SHPR), which are stable and efficiently penetrate within primary lymphocytes. Analysis of the antiviral activity of these proteins showed that one SHPR is active in both primary lymphocytes and macrophages, whereas one SHPT is active only in the latter cells. These proteins may represent prototypes of new therapeutic agents targeting the crucial functions exerted by both viral regulatory factors.     

Sensing of Barrier Tissue Disruption with an Organic Electrochemical Transistor

The gastrointestinal tract is an example of barrier tissue that provides a physical barrier against entry of pathogens and toxins, while allowing the passage of necessary ions and molecules. A breach in this barrier can be caused by a reduction in the extracellular calcium concentration. This reduction in calcium concentration causes a conformational change in proteins involved in the sealing of the barrier, leading to an increase of the paracellular flux. To mimic this effect the calcium chelator ethylene glycol-bis(beta-aminoethyl ether)-N,N,N'',N''-tetra acetic acid (EGTA) was used on a monolayer of cells known to be representative of the gastrointestinal tract. Different methods to detect the disruption of the barrier tissue already exist, such as immunofluorescence and permeability assays. However, these methods are time-consuming and costly and not suited to dynamic or high-throughput measurements. Electronic methods for measuring barrier tissue integrity also exist for measurement of the transepithelial resistance (TER), however these are often costly and complex. The development of rapid, cheap, and sensitive methods is urgently needed as the integrity of barrier tissue is a key parameter in drug discovery and pathogen/toxin diagnostics. The organic electrochemical transistor (OECT) integrated with barrier tissue forming cells has been shown as a new device capable of dynamically monitoring barrier tissue integrity. The device is able to measure minute variations in ionic flux with unprecedented temporal resolution and sensitivity, in real time, as an indicator of barrier tissue integrity. This new method is based on a simple device that can be compatible with high throughput screening applications and fabricated at low cost.     

Impact of Rapid Molecular Screening at Hospital Admission on Nosocomial Transmission of Methicillin-Resistant Staphylococcus aureus: Cluster Randomised Trial

Design

Cluster randomised crossover trial with seven wards randomly allocated to intervention or control arm.

Setting

Medical and surgical wards of a university hospital with active MRSA control programme.

Participants

All patients hospitalized >48 h in study wards and screened for MRSA on admission and discharge Intervention: Rapid PCR-based screening test for MRSA compared with control screening test by enrichment culture using chromogenic agar.

Objective

We determined the benefit of PCR-detection versus culture-based detection of MRSA colonisation upon patient admission on early implementation of isolation precautions and reduction of hospital transmission of MRSA.

Main outcome

Cumulative rate of MRSA hospital acquisition of in patients screened negative on admission.

Randomization

The sequential order of inclusion of study wards in each arm was randomised by assigning a number to each ward and using a computer generated list of random numbers.

Findings

Of 3704 eligible patients, 67.8% were evaluable for the study. Compared with culture, PCR-screening reduced the median test reporting time from admission from 88 to 11 hours (p<0.001) and the median time from admission to isolation from 96 to 25 hours (p<0.001). MRSA acquisition was detected in 36 patients (3.2%) in the control arm and 34 (3.2%) in the intervention arm. The incidence density rate of hospital acquired MRSA was 2.82 and 2.57/1,000 exposed patient-days in the control and intervention arm, respectively (risk ratio 0.91 (95% confidence interval, 0.60–1.39). Poisson regression model adjusted for colonisation pressure, compliance with hand hygiene and antibiotic use indicated a RR 0.99 (95% CI, 0.69 to 1.44).

Interpretation

Universal PCR screening for MRSA on admission to medical and surgical wards in an endemic setting shortened the time to implement isolation precautions but did not reduce nosocomial acquisition of MRSA.

Trial registration

clinicaltrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00846105","term_id":"NCT00846105"}}NCT00846105     

Outcomes of a ‘One Health’ Monitoring Approach to a Five-Year Beaver (<Emphasis Type="Italic">Castor fiber</Emphasis>) Reintroduction Trial in Scotland

The Scottish Beaver Trial, involving the translocation and release of 16 wild Norwegian beavers (Castor fiber) to Scotland, provides a good example of a ‘One Health’ scientific monitoring approach, with independent monitoring partners on ecology and public health feeding into veterinary health surveillance. Pathogen detection did not prohibit beaver release, although eight beavers were seropositive for Leptospira spp. Six deaths (37.5%) occurred during Rabies quarantine, followed by the death of two animals shortly after release and two wild-born kits due to suspected predation. Two host-specific parasites, the beaver fluke (Stichorchis subtriquetrus) and beaver beetle (Platypsyllus castoris) were also reintroduced.